Clotting on the Outer Surfaces of Vascular Catheters

Thrombotic and embolic accidents are serious complications of vascular catheterizations. Some of these complications are caused by the stripping of clot from the surface of the catheters as these catheters are withdrawn through the holes in the vascular walls (Fig. 1). The purpose of this work was to investigate the rate of clotting on the surface of various catheters and to find possible means of prevention. The catheters studied were those commonly employed in clinical catheterization, namely nonradiopaque polyethylene, nonradiopaque Teflon, radiopaque polyethylene of Swedish manufacture, radiopaque polyethylene of American manufacture, radiopaque Teflon, woven Rodriguez Alvarez coated with a “special compound,” woven directable Cordis catheters (probably covered with polyurethane), and Silastic medical grade tubing. All catheters were No. 7 French. Technic Under general anesthesia, the carotids and the jugular veins of large dogs were isolated as far as possible toward the head and toward the chest. One catheter of each kind was introduced in each vessel over a guide spring for a distance of 10 cm. These four different catheters were left in place for thirty minutes, then the animal was completely heparinized and immediately afterward sacrificed with an overdose of Nembutal. After death, the vessels were carefully opened longitudinally, taking special care not to disturb the inlaying catheters, and the catheters were gently lifted from the vessels. The clots adhering to the surface of the catheters were pushed within 1 cm of the tip of the catheters by means of sliding collars, thus simulating the effect of withdrawing the catheters through the walls of the vessels. The catheters were labeled and photographed. The clots were then separated from the catheters and weighed. Each catheter was tested twice in an artery and twice in a vein. Sixteen dogs were used in this experiment. Figure 2 shows the clots found in a typical experiment, and Figure 3 gives the average amount of clot found on 9 cm of each catheter after it had remained for thirty minutes in either an artery or a vein. The two catheters which had shown the most abundant surface clotting were then tested for thirty minutes in an artery and in a vein, counterflow and with the flow, with their lumens being flushed with injections of 5 cc of saline every five minutes. Saline flushing had no effect, and abundant surface clot was again found. Four dogs were used for this experiment. The same two catheters were placed in the same manner twice in arteries and twice in veins of four other dogs. One catheter was used now as a control while 5 cc of a heparin solution (made by adding 15 drops of a 1,000 unit per cc preparation to 100 cc of saline) was injected every five minutes through the lumen of the other catheter.